What I could think up for Disney Math (Keep in mind I am pursuing an English Ed Degree!)
Hand over your receipts or tell them at the end of the day how much you have spent on your day at the World. This would include hotel room, theme park tickets, food, goodies like souvenirs, etc. Everything. Have them chart your progress on your spending. They could make theme park and room expenditures =A and Souvenirs and Dining = B
Test Track is a good example for how to use the equation of speed. It goes 60 mph. But by substituing in letters for the items ie Car=C and Rate of Speed+A they can figure out how fast the car would be going of given longer portions of track or 2 or 3 mile difference in rate of speed. You can also do the same with the monorails, I believe they go at an average of 35 mph, the fastest clip being 40 mph. I.E if the Red Monorail leaves the TTC traveling East Ward at 35 mph it will arrive at the Magic Kingdom in how many minutes?
I think there is a fact sheet on Disney Parking Spaces per Park. If they could figure up the amount of spaces and multiply by the number of average vehicles parked there everyday, then again multiply by the number of days in operation and then by any rate increases they can figure out the amount of money spent yearly by guests on parking.
If your driving have them figure your price per gallon. If your flying same thing. Then for a carbon footprint lowering task have them figure what it would have been in Ethenol, Soy Diesel, and Natural Gas. Since Disney makes all of their own energy so as not to drain the local grid have her count the buildings on Main Street and calculate on average what their utility bill would run.
You can ask Cast Members for daily park attendance, esp if you tell them its for school. Granted you will have to usually ask the day after. BUt by calculating the number of people, percentages of adults vs. children, and then again the percentage of annual passholders versus out of state guests your kids can figure daily just based on Park Admission how much was spent on 'getting into the world'
Hope This Helps!